Mucoadhesive dosage forms for application to the oral cavity which are designed to deliver therapeutic and/or cosmetic agents to the oral mucosa are known in the art. U.S. Pat. No. 5,047,244 describes a mucoadhesive carrier allowing the controlled release of a therapeutic agent via the mucosal tissue comprising an anhydrous but hydratable polymer matrix and amorphous fumed silica. An optional water-insoluble film can be added to provide a non-adhering surface. In WO 91/06270, the same authors disclose a trilaminate film suitable for prolonged delivery of an active ingredient in the oral cavity.
In a similar way, U.S. Pat. No. 4,876,092 discloses a sheet-shaped adhesive preparation comprising an adhesive layer containing certain water-soluble and water-insoluble polymers and a water-insoluble carrier which can adhere to the oral mucosa thereby releasing an active agent to the oral cavity. All the devices so far cited are not completely water soluble and will stay in the oral cavity even after the therapeutic goal has been achieved leaving the patient with a certain discomfort in the mouth resulting mainly from the support layer which leaves an insoluble residue in the mouth.
A number of attempts have been made to reduce the adverse feeling in the oral cavity caused by the rigidity and inflexibility of the support layer by introducing soft film supports. EP 0 200 508 B1 and EP 0 381 194 B1 disclose the use of polyethylene films, polyvinyl acetate, ethylene-vinyl acetate copolymers, metal foils, laminates of cloth or paper and a plastic film, and similar materials as soft film supports, whereby synthetic resins like polyethylene, vinyl acetate homopolymers, and ethylene-vinyl acetate are the preferred materials. In a similar way, CA 1 263 312 discloses the use of polyolefines such as polyethylene, polypropylene, polyesters, PVC, and non-woven fabrics as soft support materials.
However, these devices still leave the patient with a considerable amount of residue from the water-insoluble support film thereby still causing a feeling of discomfort. The obvious solution to overcome this problem was to develop mucoadhesive films which completely disintegrate, or even completely dissolve in the saliva. Fuchs and Hilmann (DE 24 49 865.5) prepared homogeneous, water-soluble films intended for buccal administration of hormones. They proposed the use of water-soluble cellulose-derivatives, like hydroxyethyl cellulose, hydroxypropyl cellulose, or methyl hydroxypropyl cellulose, as film forming agents.
Both DE 36 30 603 and BP 0 219 762 disclose the use of swellable polymers such as gelatins or corn starch as film forming agents, which upon application to the oral cavity, slowly disintegrate, thereby releasing an active ingredient incorporated in the film. The same polymers can also b used to prepare films which are intended for dental cleansing, as described in EP 0 452 446 B1.
These preparations still create an adverse feeling in the mouth which is mainly caused by their initial rigidity and delayed softening. Thus, there has still been a demand for a composition for use in the oral cavity which meets the requirement of providing a pleasant feeling in the mouth. The present invention discloses methods and compositions that are capable of avoiding an adverse feeling by providing the film which is intended for application to the oral mucosa with instant wettability, while achieving adequate tensile strength in the free film to allow for easy coating, converting, and packaging of a consumer-friendly product.